Calcium Channel Blockers (CCBs)

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They are separated into by their chemical makeup. I don’t think it is important to remember the class name or that it is a chemical makeup of the drug but I think it is important to know that they are different and which one is used is based on chemical makeup because there are different indications and side-effects. Below I listed them for classification purposes:

Calcium Channel Blocker Classification

Phenylalkylamine– Verapamil

Used primarily to treat angina by reducing the heart’s oxygen demand and reversing coronary vasospasms.

Works by decreasing the force of contraction in the heart (not by vasodilating)

Contraindicated with beta-blockers

Benzothiazepine– Diltiazem

The mechanism of action is mix between Phenylalkylamines and Dihydropyridines.

Works by vasodilating and decreasing the force of the heart.

Dihydropyridines-(end in -dipine)

This class of CCBs is most selective for smooth muscle (meaning going to decrease systemic vascular resistance) and used primarily for hypertension.

Sometimes this can cause hypotension and this leads to the heart speeding up to fulfill the body’s oxygen demand. This is called reflex tachycardia.

There are three generations of Dihydropyridines:

1st generation

Nifedipine

2nd generation

Nicardipine

Felodipine

Isradipine

3rd generation

Amlodipine

How do Calcium Channel Blockers work?

When a CCB is distributed into the bloodstream and flows to the heart, it attaches to the calcium channels. This stops/slows the calcium from flowing through cell walls into the cells. Calcium channels are found in abundance at the SA and AV nodes as well as in cardiac myocytes, and smooth muscle cells.

SA and AV nodes are the pacemakers of the heart, so if your patient has tachycardia due to a problem above the ventricles (supraventricular) then a CCB may help. When calcium is slowed from crossing into the SA or AV node cells, electrical activity will slow down, decreasing the rate of impulses being sent out to contract the heart. This will inherently increase the refractory period of the AV node (increasing the PR interval) and decreasing ventricular response.

Smooth muscle cells found around blood vessels control vasodilation and constriction. Blocking calcium intake into the cell relaxes the smooth muscle, opening up the blood vessel and decreasing blood pressure.

Smooth muscle is also located in your GI tract and slows down your gut motility. So these patients can have constipation.

Note: Skeletal muscle uses sodium influx for contraction, not calcium, and is not affected by CCBs.

Calcium Channel Blocker Uses and Indications

Now that we know what Calcium Channel Blockers do, it should be pretty easy to answer the question: Why would I administer a calcium channel blocker to my patient?

Answer: If they have high blood pressure or a fast heart rate, you would administer a CCB.

For example in these conditions:

Hypertension

Because it decreases BP

Angina

Vasodilation will help get blood through any partially occluded vessels so if the chest pain is from decreased blood flow to a part of the heart, CCBs will open up the vessel more and allow more blood to get through

Supraventricular tachycardias

Because it decreases heart rates and works at the SA and AV nodes so if the rhythm is above the ventricles it is likely occurring from the SA or AV nodes and this will decrease the stimulus, thus decreasing the heart rate

Administration of a Calcium Channel Blocker

A Calcium Channel Blocker can be administered orally or intravenously. You will not be administering oral CCBs in an emergency but you might administer IV CCBs in a non-emergency.

Giving IV Calcium Channel Blockers:

Verapamil

5-10 mg IV push over 2 minutes

Diltiazem

Stand alone bolus:

25mg/kg over 2 minutes

Bolus followed by infusion:

Usually 10-20 mg over 2 minutes

Infusion:

5-10 mg Infusion with bolus (see dose above)

Increase by 5-10 mg every 15 minutes as needed until desired heart rate and BP are reached.

When giving a Calcium Channel Blocker you should monitor heart rate, blood pressure, and digoxin levels. This is because of the potential of the BP bottoming out, heart rate slowing down too much and of course this medication makes digoxin levels higher. So keep your eye on your patients dig levels if they take digoxin.

Calcium Channel Blocker Side Effects

Increases Digoxin levels

Digoxin also binds to the same calcium channels that CCBs do, except that CCBs have a stronger affinity, kicking digoxin off the binding site and causing potentially lethal serum digoxin levels.

Constipation

Remember smooth muscle involvement!

Hypotension

Smooth muscles relaxing causing dilation.

Bradycardia

Slowing conduction through the SA and AV nodes

AV node block

When the blocked channels completely stop the AV node from communicating to the ventricles. The purkinje fibers will take over as the pacemaker at this time so the heart rate will be slowwwww (20-40 bpm).

Congestive Heart Failure

Patients with CHF need to have an increase in the force of contraction. So decreasing the force of action plus vasodilation will compound the CHF.

Edema

Vasodilation will increase edema because it makes the capillaries leaky, making the surrounding tissues fill up with fluid.

Heartburn

The smooth muscles being relaxed can cause the esophagus to relax too, meaning GERD.

Headache

From vasodilation, increase in blood flow can cause headaches (like with nitroglycerin!)

Flushing

From vasodilation, increasing in blood flow to the surface of the skin.

Calcium Channel Blocker Overdose

Any calcium channel blocker overdose is serious, however, the most concerning (and most lethal) to overdose on are verapamil and diltiazem because they inhibit metabolism leading to a long half life.

CCB overdose is no joke because the medications usually have a sustained release action as well. So if symptoms start to occur, they will continue to get worse because there is more of the medication to be released.

Then have an insulin drip start at 0.5 Units/kg/hr and titrate up every 30 minutes up to 5 Units/kg/hr.

Can be up to 850 units/hr of insulin!!! Yeah you read that right. Insulin therapy is aggressive

Closely monitor patient glucose levels and add IV glucose such as D5W as needed to help the patient have normal serum glucose levels

Consider activated charcoal if very early in process and the patient is asymptomatic.

If it is an extended release (ER) than it can be up to 4 hours after ingestion of the CCB

If it is not an ER medication than you can administer activated charcoal up to one hour after ingestion, safely.

Calcium Channel Blocker Contraindications and Considerations

Calcium Channel Blockers (CCBs) should be given with caution in patients with kidney disease because the kidneys excrete out the medication. So if the kidneys are not working, the CCBs will stay in the blood and body.

Make sure you have obtained an EKG before administering a CCB to someone who has never had this medication. If you are administering the medication IV, get an EKG regardless if they take the medication at home or have had the medication before. You are looking for AV block (second or third-degree heart block) and sick sinus syndrome on the 12 lead ECG/EKG. If the patient has AV block or sick sinus syndrome, do not give this medication.

Take vital signs prior to administering this medication. If the patient’s blood pressure or heart rate are low, hold the medication.

Withdrawing CCBs needs to be done in a slow and controlled manner because a patient can revert to dangerous arrhythmias if discontinued abruptly.

Also, do not give with grapefruit juice. I threw this in there because as a nurse, you may need to teach the patient to not do this. Side note: if you work in a hospital that serves grapefruit juice, I want to hear about the other fancy things you have so please leave a comment and let me know.

Long-term considerations for Calcium Channel Blockers

Patients who are on calcium channel blockers will likely need BP and heart rate monitoring by the primary care team. The patient may also need to be prophylactically treated for constipation (remember CCBs slow down gut motility because they attach to the smooth muscles in the intestines).